Watershed Algorithm source - bug

Posted by David Pont on Mar 24, 2011; 10:16pm
URL: http://imagej.273.s1.nabble.com/Watershed-Algorithm-source-bug-tp3685192.html

I recently found source code for the Watershed Algorithm Plugin for ImageJ at the RSB web site

For the record -
After a google search I found a link to the source on a Wikipedia page:

http://en.wikipedia.org/wiki/Watershed_%28image_processing%29

which linked to a page hosted at the RSB web site here:
http://rsbweb.nih.gov/ij/plugins/watershed.html

I ported the code to Python and carried out some tests by processing the same input image through ImageJ and my code. I found a bug which caused incorrect location of watershed boundaries.
The bug appears in the original Java code I obtained from the RSB site. It seems likely that it has been found and fixed earlier, as it does not manifest in ImageJ. I suppose the code I got from the RSB site is out of date with respect to the current code for the Watershed Algorithm plugin in ImageJ.

The bug is fixed by changing line 160 in Watershed_Algorithm.java
from:
                                    if( (q.getDistance() <= curdist) &&
to:
                                    if( (q.getDistance() < curdist) &&


regards, Dave



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